The process of manufacturing a semiconductor device includes various processes, such as a lithography process, an etching process and an ion implantation process. After completion of each process, a cleaning process and a drying process for removing impurities and residues remaining on a wafer surface to clean the wafer surface are performed before the transfer to the next process.
In recent years, as progress has been made in miniaturization of elements, a problem has arisen in that, during development and drying of resist patterns after the lithography process (exposure and development), the resist patterns are collapsed due to capillarity. To solve such a problem, a method of making the surfaces of resist patterns water-repellent to decrease capillary forces acting between the resist patterns and developer as well as between the resist patterns and pure water for rinsing has been proposed (see, e.g., Japanese Patent Application Laid-Open No. 7-142349). Under this method, an organic matter is adhered onto the surfaces of resist patterns; however, the organic matter is removed together with the resist patterns in the etching process after the lithography process.
For example, in cleaning treatment of a wafer after the etching process, a chemical for the cleaning treatment is supplied onto the surface of the wafer, and then pure water is supplied to perform rinsing. After the rinsing, drying is performed which removes the pure water remaining on the wafer surface and dries the wafer.
As the method of performing the drying, there is known a method which uses isopropyl alcohol (IPA) and substitutes IPA for pure water on a wafer to dry the wafer (see, e.g., Japanese Patent No 3866130). However, there has been a problem in that, during the drying, the actual device patterns formed on the wafer are collapsed by the surface tension of a liquid. Even with hydrofluoroether (HFE) having lower surface tension than IPA, it has been difficult: to restrain the pattern collapse.
To solve such problems, supercritical drying in which the surface tension becomes zero has been proposed. However, it is difficult to apply the supercritical drying to mass production processes. Further, the supercritical drying has had a problem in that, when moisture or the like is carried into a chamber which provides a supercritical atmosphere, collapse of patterns cannot be prevented.